1. Field of the Invention
The present invention relates to a wire-and-thread rimmed frame for eyeglasses, which frame uses lengths of high-tension thread fixed to its upper wire half-rims to hold two lens in a pair of glasses.
2. Related Arts
A wire-and-thread rimmed frame has two lengths of high-tension thread fixed to its upper wire half-frames for holding the opposite lenses. Use of upper wire half-rims permits reduction of the eyeglass frame in weight and expansion of visual field. FIG. 9 shows a conventional wire-and-thread rimed frame structure. As shown, each semi-circular wire rim "a" has a length of high-tension thread "b" fixed to its opposite ends, thus enabling the lens "c" to be fixedly held within the wire-and-thread loop. The opposite upper half-rims "a" are jointed by the bridge "d", and each half-rim "a" has a joint piece "e" fixed to its outer edge. Each temple is hinged to one or the other half-rim "a" via the joint piece "e" so that the temple may be folded or unfolded relative to the front of the frame.
In order to expand the visual field a length of six millimeter-thick wire is used to form the upper half-rims "a". Each upper half-rim "a" is fitted in the groove made in the circumference of the lens "c". A length of high-tension thread such as nylon thread is fitted in the circumferential groove of the lens "c", too. That is to say the thickness of the wire is adjusted to the external diameter of the thread. Such wire which is thin enough to fit in the circumferential groove of the lens "c", however, can be hardly strong enough to provide an eyeglass frame for practical use. As the rim wire is fitted in the circumferential groove of the lens "c", some parts such as a bridge "d" connecting the opposite half-rims "a", joint pieces "e" for connecting temples to the half-rims and butterfly-wing pieces for connecting nose pads cannot be soldered to the rim wire, which is in the circumferential grooves of the opposite lenses.
In practice, each upper wire half-rim "a" has proximal and distal reinforcement pieces "f" soldered to its opposite sides. Then, the bridge "d" is soldered to the proximal reinforcement pieces "f " appearing on the circumferences of the opposite half-rims "a". Likewise, the joint pieces "e" are soldered to the distal reinforcement pieces "f" of the opposite wire half-rims. The proximal or distal reinforcement piece "f", however, has an increased strength, compared with the thin rim wire. Consequently the inner stress is likely to converge to the boundary "g" between the half-rim "a" and the proximal or distal reinforcement piece "f", resulting in the breaking of the eyeglass frame at these restricted places. As a matter of fact the rim wire was locally heated and softened when the proximal or distal reinforcement piece was soldered to the rim wire, thus reducing the strength of the rim wire at these restricted places. Sometimes, the lens "c" is unduly loaded there to cause cracks in the lens "c".
A length of high-tension thread "b" is inserted in two holes made in each of the proximal and distal reinforcement pieces "f" to be fixed thereto. Then, the length of high-tension thread "b" is stretched so that it may be caught and somewhat deformed by the circumferential edge "h" of each hole to be positively fixed to the reinforcement piece, as seen from FIG. 10 which shows Part "B" in FIG. 9 at an enlarged scale. As a result the length of high-tension thread "b" is liable to be broken there.
The same applicant as the present application filed a patent application on Aug. 25, 1997 in Japan (Japanese Patent 11-2752(A)), proposing that a length of high-tension thread has two loops formed at its opposite ends, thereby permitting the length of high-tension thread to be caught by the hook ends of the upper half-rim. There is no fear for causing any breaking in the length of high-tension thread. The length of high-tension thread is guaranteed to be free of loosing, and therefore, there is no fear of allowing the lens to slip off from the front of the eyeglass frame.
In the so proposed eyeglass frame, however, it is still necessary to solder a joint piece to the outer edge of each half-rim. Also, a nose pad attachment piece needs to be soldered to the inner edge of the half-rim. The soldering will cause the half-rim wire to be locally softened. Each temple is hinged to the joint piece, which is soldered to the half-rim. The temple is liable to be loosely fixed when the screws are loosened in the hinge.